# all_permutations_by_length.py

# all_permutations_by_length.py

def permutations(l, n, str_a=''):
    if len(str_a) == n:
        print str_a
    else:
        for c in l:
            permutations(l, n, str_a+c)

zzz = permutations("ABC", 3)

'''
output...

AAA
AAB
AAC
ABA
ABB
ABC
ACA
ACB
ACC
BAA
BAB
BAC
BBA
BBB
BBC
BCA
BCB
BCC
CAA
CAB
CAC
CBA
CBB
CBC
CCA
CCB
CCC
'''